The Builder Mod for 1.5.2 lets you instantly spawn different structures. All of these buildings can be created using 3 new themed seeds. These seeds can then be activated using different items.
Unique Homes:
Tree House:
Snow Man:
Sand Castle:
Igloo:
Hobbit Home:
Tree House -Hammer
Snow...

The OceanCraft mod for Minecraft 1.5.2 makes your oceans more active by adding new mobs, plants, and blocks to your oceans. You can use these new materials to to craft new items that make exploring your oceans better.
New Mobs:
Fish:
Drops fish when killed.
Whale:
Friendly, but hard to kill. Drops fish when killed.
Manta Ray:
Drops fins when killed.
Crab:
A hostile mob that drops a crab shell when killed.
New Blocks:
Seaweed:
Can be used in new crafting recipes.
Coral:
Sponge:
Shells:
Spawns on the beach.
New Items:
Water Pearl:
Allows you to breathe underwater for up to 4 minutes.
Coral Armor:
Although not as strong as diamond,...

The Rail Guns mod is a simple mod for 1.5.2 that adds a new gun that makes placing tracks easier. The Rail Gun digs tunnels and place rails down automatically.
Rail Guns Mod Usage:
The Gun consumes the rails from your inventory and automatically digs a 3*3 hole in the wall while placing rails in the center of the tunnel!
Recipe:
The gun will use the type of rail that was used to craft the gun.
Download Rail Guns Mod for 1.5.2:
Rail Gun Mod for 1.5.2
Modloader for 1.5.2
Installation:
Find your Minecraft.jar file.
Open Minecraft.jar using Winrar and delete the META-INF folder
Drag the files from the modloader and Rail Gun zip file...

This mod for 1.5.2 adds quicksand for the game. It spwans naturally and can be crafted. It is perfect for traps, defenses, mazes, and more and is compatible with multiplayer servers.
Quicksand Mod Features:
Quicksand naturally spawns in swamps and on beaches. When a player or mob steps on quicksand it will sink down unless it can dig itself out. Quicksand will fall if unsupported like regular sand.
Dry quicksand can be found in deserts. It is non-solid, meaning you just fall into it. It is easier to get out of, but also easier to stumble into. Because it looks a lot like regular sand, it is great for traps.
Download Quicksand Mod for...

The Arcane Scrolls mod for 1.5.2 adds 4 types of scrolls to the game that will assist you. They are Utility (Green), Offensive (Red), Defensive (Blue), and Special (Purple) scrolls. They can be used to teleport you, make you move and fight faster, and destroy hostile mobs around you.
Arcane Scrolls Mod Features:
New Items:
Name: Arcane Ore
Found around the world, when mined it will give you one arcane stone.
Name: Arcane Stone
Allows you to craft the arcane tome and is used as energy when using scrolls.
Utility Scrolls:
Name: Scroll of Vitality
Info: Heals 5 1/2 hearts.
Unlock level: 5
Charge Usage: 10
Name: Scroll of Feeding
Info: Restores...

The Buddy Mod for 1.5.2 adds a buddy to Minecraft. This buddy follows the player around and unlike wolves, cannot die. It can take any shape and can be named. It can also be picked up and carried around on your head.
Buddy Mod Features:
– The buddy will spawn with the last model used...